Thomas G. Upshaw and Martha Ann "Mattie" Roark

I am hoping someone will have a little more information about Thomas G. Upshaw, born 31 March 1851; married Martha Ann Roark on 22 April 1873 at her father John Roark's residence in Franklin Co. Arkansas. They had 3 children: John Thomas, William Harley, and Ella. He is buried in Franklin Co. Arkansas in the same cemetary as his father-in-law John Roark. After his death in 1885, Mattie remarried, to a William C. Harp. All this is well documented. What ISN'T is Thomas G.'s ancestry. Some trees have him confused with Thomas J. Upshaw, son of Middleton and Lucy Ann. Thomas J. was born in 1849 and he also married a woman named Martha Ann (Loid) in Arkansas in 1872. I suspect that Martha Ann Roark was called "Mattie" to distinguish her from the Martha Ann who was already in the family, having married Thomas J. Upshaw the previous year. Where did Thomas G. Upshaw come from? Is he a half-sibling/illegitimate child? He doesn't appear anywhere before his married to Martha Ann Roark, except maybe an entry in the 1870 census from Lower, Franklin AK which has a Thomas Upshaw, born in Georgia about 1851. I searched Henry Cross for some connection to the Upshaws and found a lot of information about him and his family but I couldn't find any connection other than both families were from Georgia and moved to Arkansas. One family tree at ancestry.com has DNA test attached to the descendents of Thomas G. Upshaw but the DNA results say "Thomas J". Can anyone help out?